Bottom Line:
Using gene chip analysis, we detected that myofibroblast Thy1 crosslinking mediates downregulation of genes promoting cell proliferation, survival, and differentiation, and reduces production of extracellular matrix (ECM) components, while concurrently mediating the upregulation of genes known to foster inflammation and immunological functions.Lung myofibroblasts downregulate Thy1 expression to increase their proliferation but to diminish the in vivo inflammatory milieu.Inflammation is not essential for evolution of fibrosis as was previously stated.

ABSTRACTLung fibrosis is characterized by abnormal accumulation of fibroblasts in the interstitium of the alveolar space. Two populations of myofibroblasts, distinguished by Thy1 expression, are detected in human and murine lungs. Accumulation of Thy1-negative (Thy1(-)) myofibroblasts was shown in the lungs of humans with idiopathic pulmonary fibrosis (IPF) and of bleomycin-treated mice. We aimed to identify genetic changes in lung myofibroblasts following Thy1 crosslinking and assess the impact of specific lung myofibroblast Thy1-deficiency, in vivo, in bleomycin-injured mouse lungs. Thy1 increased in mouse lung lymphocytes following bleomycin injury but decreased in myofibroblasts when fibrosis was at the highest point (14 days), as assessed by immunohistochemistry. Using gene chip analysis, we detected that myofibroblast Thy1 crosslinking mediates downregulation of genes promoting cell proliferation, survival, and differentiation, and reduces production of extracellular matrix (ECM) components, while concurrently mediating the upregulation of genes known to foster inflammation and immunological functions. Chimeric Thy1-deficient mice with Thy1(+) lymphocytes and Thy1(-) myofibroblasts showed fibrosis similar to wild-type mice and an increased number of CD4/CD25 regulatory T cells, with a concomitant decrease in inflammation. Lung myofibroblasts downregulate Thy1 expression to increase their proliferation but to diminish the in vivo inflammatory milieu. Inflammation is not essential for evolution of fibrosis as was previously stated.

fig1: Thy1-positive total lung cells are increased during experimental fibrosis; however, the proportion of myofibroblasts that are Thy1-positive is decreased. (A) Immunohistochemistry of Thy1 staining (arrows), in the lungs of saline- vs. bleomycin-treated mice, 14 days following instillation. Representative results. (B) Lung myofibroblasts were isolated from control saline-treated (Ctrl) and bleomycin-treated mice at 1, 3, 7 and 14 days following IT. A graphical presentation of Thy1 expression FACS analysis was performed using PE-conjugated anti-Thy1 (CD90) mAb. The differences between control (Ctrl) saline-treated and bleomycin-treated mouse lung myofibroblasts on day14 were significant. ∗P < 0.05, n = 4. (C) Histogram plot showing a representative result of assessment of Thy1 expression in myofibroblasts from control (Ctrl) saline-treated mice compared to Thy1 expression in myofibroblasts from bleomycin-treated mice at day 14 following IT. Results were similar in 2 different experiments (n = 4).

Mentions:
Thy1 expression was assessed by immunohistochemistry in frozen lung tissue sections of saline- and bleomycin-treated mice 14 days following instillation, the point of peak fibrosis [4]. When compared to saline-treated mice, Thy1 expression in the total lung was increased following bleomycin instillation (Figure 1(a)).

fig1: Thy1-positive total lung cells are increased during experimental fibrosis; however, the proportion of myofibroblasts that are Thy1-positive is decreased. (A) Immunohistochemistry of Thy1 staining (arrows), in the lungs of saline- vs. bleomycin-treated mice, 14 days following instillation. Representative results. (B) Lung myofibroblasts were isolated from control saline-treated (Ctrl) and bleomycin-treated mice at 1, 3, 7 and 14 days following IT. A graphical presentation of Thy1 expression FACS analysis was performed using PE-conjugated anti-Thy1 (CD90) mAb. The differences between control (Ctrl) saline-treated and bleomycin-treated mouse lung myofibroblasts on day14 were significant. ∗P < 0.05, n = 4. (C) Histogram plot showing a representative result of assessment of Thy1 expression in myofibroblasts from control (Ctrl) saline-treated mice compared to Thy1 expression in myofibroblasts from bleomycin-treated mice at day 14 following IT. Results were similar in 2 different experiments (n = 4).

Mentions:
Thy1 expression was assessed by immunohistochemistry in frozen lung tissue sections of saline- and bleomycin-treated mice 14 days following instillation, the point of peak fibrosis [4]. When compared to saline-treated mice, Thy1 expression in the total lung was increased following bleomycin instillation (Figure 1(a)).

Bottom Line:
Using gene chip analysis, we detected that myofibroblast Thy1 crosslinking mediates downregulation of genes promoting cell proliferation, survival, and differentiation, and reduces production of extracellular matrix (ECM) components, while concurrently mediating the upregulation of genes known to foster inflammation and immunological functions.Lung myofibroblasts downregulate Thy1 expression to increase their proliferation but to diminish the in vivo inflammatory milieu.Inflammation is not essential for evolution of fibrosis as was previously stated.

ABSTRACTLung fibrosis is characterized by abnormal accumulation of fibroblasts in the interstitium of the alveolar space. Two populations of myofibroblasts, distinguished by Thy1 expression, are detected in human and murine lungs. Accumulation of Thy1-negative (Thy1(-)) myofibroblasts was shown in the lungs of humans with idiopathic pulmonary fibrosis (IPF) and of bleomycin-treated mice. We aimed to identify genetic changes in lung myofibroblasts following Thy1 crosslinking and assess the impact of specific lung myofibroblast Thy1-deficiency, in vivo, in bleomycin-injured mouse lungs. Thy1 increased in mouse lung lymphocytes following bleomycin injury but decreased in myofibroblasts when fibrosis was at the highest point (14 days), as assessed by immunohistochemistry. Using gene chip analysis, we detected that myofibroblast Thy1 crosslinking mediates downregulation of genes promoting cell proliferation, survival, and differentiation, and reduces production of extracellular matrix (ECM) components, while concurrently mediating the upregulation of genes known to foster inflammation and immunological functions. Chimeric Thy1-deficient mice with Thy1(+) lymphocytes and Thy1(-) myofibroblasts showed fibrosis similar to wild-type mice and an increased number of CD4/CD25 regulatory T cells, with a concomitant decrease in inflammation. Lung myofibroblasts downregulate Thy1 expression to increase their proliferation but to diminish the in vivo inflammatory milieu. Inflammation is not essential for evolution of fibrosis as was previously stated.